Skeletal structures are kinematically acted upon by muscles. Therefore, the role of muscles in skeletal health is remarkable. The health and development of musculoskeletal structures begin in childhood. Axial and appendicular muscle strength in boys and girls is about the same until age 10 years, when a discrepancy begins to develop [5]. One study showed that back pain can develop in children who have low back strength [6]. Reduction of muscle strength is affected by the aging process in men and women. Sarcopenia affects type II fibers (“fast twitch”) more than type I fibers. This expands the type I motor neuron units at the expense of type II fibers [7]. The consequences of these changes are less muscle strength and agility and the reduction in endurance for daily activities that comes with age (Figure 7.3) [8].

In the matter of age-related challenges, women are more affected than men since they initially have lower muscle strength than men [8]. In that study, back and upper and lower extremity muscle strengths were measured in healthy men and women aged 20 to 89 years. Comparison of the two sexes showed that women’s muscle strength was lower than men’s at all ages. Indeed, the back extensor strength of women at different decades ranged from 54% to 76% that of men.

Along with disequilibrium, muscle and bone loss becomes challenging. Axial muscle strength decreases by about 50% from age 30 to 80 in women, and by age 80, women lose about 50% of axial bone mass [9]. The combination makes women more predisposed to osteoporosis and fragility than men. Furthermore, in both sexes, the amount of body sway increases with reduction of proprioception and increased propensity for falls. This results in reduced participation in PA with aging (Figure 7.4) [10]. Kyphosis can increase the risk (and fear) of falls in osteoporotic individuals [11, 12]. It can also decrease vital capacity of the lungs and contribute to back pain due to mechanical strain [13].

Comprehensive successful management of osteoporosis requires a combination of the Rehabilitation of Osteoporosis Program-Exercise (ROPE) and pharmacotherapy as needed. Antiresorptive agents (to reduce bone loss) and anabolic agents (to build bone) have each been more effective for increasing bone mass and decreasing bone fracture when combined with ROPE. The choice of pharmacotherapy depends on the status of the patient’s overall health, status of bone cells, BMD, and fragility.

The objective of using exercise in the treatment of osteoporosis is to improve muscle strength for axial and appendicular stability and to induce proper mechanical strain for maintenance of bone health. Therefore, a strengthening exercise program specifically for back extensors and upper and lower limbs is recommended (Figure 7.5). A back extension exercise program specific to one’s musculoskeletal competence and pain status can be performed in a sitting position and later advanced to the prone position (Figure 7.5). When fragility is resolved, back extension is performed against resistance applied to the upper back. To decrease pain and immobility present in acute vertebral fracture, the use of spinal orthoses becomes inevitable. Therapeutic exercise should address osteoporosis-related deformities of axial posture, which can increase risk of falls and fractures.

Strengthening of the major appendicular muscles decreases fragility andimproves participation in PA. The effect of strengthening exercises is augmented by proper intake of cholecalciferol and calcium. Thus, the role of a therapeutic exercise program is to increase muscle strength safely, decrease immobility-related complications, and prevent falls and fractures. As with pharmacotherapy, therapeutic exercises need to be prescribed.

Exercise intensity in patients with established osteoporosis is closely based on bone density and muscle strength. Neuromuscular, cardiovascular, and general health also play a substantial role in initiating the program; these health considerations are reviewed to avoid further exercise-induced injury.

There are common definitions of bone density [14]. In general, BMD evaluation and T-scores of the spine and hips define the severity of osteoporosis. A T-score of −1 to −2.5 indicates osteopenia, and a T-score less than −2.5 indicates osteoporosis. If a vertebral fracture is present, osteoporosis is then considered severe. To apply safe mechanical forces to the bone, we need to consider that without mechanical strain, differentiation of osteogenic precursors to osteoprogenitor cells will be suppressed, and the osteoprogenitor cells could change into adipocytes. The adaptability observed between adipocyte and osteoblast differentiation is necessary for bone formation under mechanical strain [15].

We have observed several patients with weak/deconditioned back muscle strength who suffered vertebral fracture despite a BMD score above −2.5. On the other hand, several patients with strong back muscle strength and BMD below −2.5 did not demonstrate vertebral fracture. Thus, the role of muscle strength in the prevention of vertebral fracture could be of great significance [16].

Tables 7.1, 7.2, and 7.3 were developed to facilitate the consideration of different exercise programs without overstraining when BMD is low and in the presence of fragility. These tables provide some guidelines for planning an exercise program with consideration of BMD, muscle strength, cardiovascular fitness, and neuromuscular health status.

A positive correlation exists between strength of back extensors and BMD of the spine (Figure 7.6) [17]. In a back exercise study, participants’ activities of daily living, posture, and body shape improved with exercise [18]. A study from the author and coinvestigators shows that several factors, including age, grip strength, and kyphosis, affect the level of PA and quality of life in patients with postmenopausal osteoporosis [19]. Statistical analysis has shown that back extensor strength, which is mainly provided by lumbar extensors, and lumbar spinal mobility are the most important factors for improving quality of life [19].

Loading of the spine through lifting weight in the upper extremities needs to be done with proper technique, as shown in Figure 7.5 [20]. Back extension exercises from a prone position with weight applied to the upper back improves back strength considerably, and the effect has been shown to last for years [16]. In addition, if performed properly, the exercise itself does not cause back pain [21]. Back extensor strengthening exercise can decrease the risk of vertebral fracture after vertebroplasty (Figure 7.7) [22]. Improvement of axial muscle support improves posture and helps reduce the risk of vertebral fracture as well as falls. The major supportive muscles are extensors (more than flexors); the ratio of strength is about 2/1.5:1 [23]. Spinal extension exercises should be used along with exercises to reduce lumbar lordosis [24, 25]. One study showed that progressive resistive back-strengthening exercises can improve back strength considerably. A recent randomized controlled trial showed the most effective, safe back-strengthening exercise to be the method of Sinaki et al [26]. However, according to several other studies, the most effective back-strengthening exercise continues to be progressive resistive back extension exercises [27–29]. Weakness of the abdominal muscles is fairly common, and in cases of osteopenia or osteoporosis, this can be addressed with modified isometric strengthening such as partial lift of the trunk rather than strenuous flexion of the spine (Figure 7.5). Strenuous spinal flexion during daily activities and spinal flexion exercises need to be avoided in patients with osteoporosis (Figure 7.2) [4]. In that study, which compared the effect of flexion and extension exercises on the spine, it was demonstrated that even without pharmacotherapy, patients with osteoporosis who performed back extension exercises had a considerably lower rate of fracture than those who performed spinal flexion exercises or no exercise. This issue again became a concern when several patients who were in good health, but had osteopenia, suffered vertebral compression fracture when they participated in yoga spinal flexion position exercises (Figure 7.8) [30].